JP2005293750A - Method and device for recording and reproduction, and magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for recording and reproduction, and a magnetic recording medium which are suitable for high recording density. <P>SOLUTION: Equalization and modulation are performed under a condition expressed by an expression (1) or (2) including coefficient terms (1, a1, a2, ..., am (m=2n or 2n+1, where (n) is an integer of ≥1)) of a partial response when γ showing asymmetry of an isolated inverted waveform reproduced from the magnetic recording medium is >0 or under a condition represented by an expression (3) or (4) including the coefficient values of the partial response when γ is <0. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a recording / reproducing method, a recording / reproducing apparatus, and a magnetic recording medium, and more particularly to a recording / reproducing method, a recording / reproducing apparatus, and a magnetic recording medium suitable for a high recording density magnetic recording medium.

  In recent years, there has been a remarkable improvement in recording density in magnetic recording media such as magnetic recording tapes and magnetic disks. For this reason, various techniques relating to recording / reproducing apparatuses have been proposed and put into practical use in response to the increase in recording density of recording media. For example, various technologies have been proposed and put into practical use for adopting an MR head as a recording / reproducing head and improving an interface between a recording medium and the head. Furthermore, in terms of signal processing technology, the partial response (PR) method and the maximum likelihood decoding (ML) method are combined in order to compensate for the degradation of the S / N ratio accompanying high-density recording. The PRML system has been put into practical use in a recording / reproducing apparatus using a recording medium such as a magnetic disk, a digital VTR, a computer backup magnetic tape, an optical disk (see Patent Document 1). In this PRML signal processing method, PR4ML (PR (1, 0, -1) ML), EPR4ML (PR (1, 1, -1, -1) ML) are selected according to the number of terms of the signal sequence to be equalized. Various methods such as EEPR4ML (PR (1, 2, 0, -2, -1) ML), EEEPR4ML (PR (1, 3, 2, -2, -3, -1) ML) are known. Yes.

If an optimum partial response signal process is applied according to the characteristics of the magnetic material used, it is effective because an information signal recorded at a high density on the magnetic recording medium can be restored at a low error rate. For example, a magnetic recording medium having a magnetic layer containing hexagonal ferrite as a magnetic material has characteristics of high reproduction output in high-density recording and low noise. However, because hexagonal ferrite has a magnetization component in the vertical direction even in in-plane orientation or non-orientation due to its crystal structure, the isolated inversion reproduction waveform is perpendicular to the in-plane orientation inversion reproduction waveform. A unique waveform obtained by adding the isolated and inverted reproduction waveforms, for example, an asymmetric waveform as shown in FIG. Conventional PRML signal processing optimized for a magnetic recording medium in which in-plane magnetization is recorded is applied to a unique isolated inversion reproduction waveform obtained when such hexagonal ferrite is used as a magnetic material. However, the characteristics peculiar to the hexagonal ferrite magnetic material that the optimum signal processing cannot be performed, the reproduction output in high-density recording is high, and the noise is low cannot be utilized.
JP 2002-157827 A (paragraph 0051, FIG. 10)

  Accordingly, an object of the present invention is to provide a recording / reproducing method and a recording / reproducing apparatus that are optimized for a partial response signal processing system when reproducing an information signal from a magnetic recording medium having a high recording density.

In order to solve the above problems, the present invention provides a recording / reproducing method for reproducing an information signal recorded on a magnetic recording medium by equalizing and demodulating the information signal using a partial response signal processing method. When γ indicating the asymmetry of the reproduced waveform has a waveform with γ> 0, the coefficient terms of partial response (1, a ₁ , a ₂ ,..., A _m (m = 2n or 2n + 1: n is When the waveform satisfying the following formula (1) or formula (2) satisfies the following formula (1) or formula (2) and γ is γ <0, the partial response coefficient term is the following formula (3) or Provided is a recording / reproducing method characterized by performing equalization demodulation under a condition satisfying Expression (4).

In this recording / reproducing method, partial response coefficient terms (1, a ₁ , a ₂ ,..., A _m (m = 2n or 2n + 1) are selected according to the asymmetry of the isolated inverted reproduction waveform reproduced from the magnetic recording medium. : N is an integer of 1 or more) so that the sum of the first half term and the sum of the second half term satisfy the above formula (1) and formula (2) or the above formula (3) and formula (4), etc. By optimizing and demodulating, it is possible to apply PRML signal processing optimum for the characteristics of the hexagonal ferrite magnetic material.

The present invention also relates to a recording / reproducing apparatus having an equalizing means for equalizing an information signal recorded on a magnetic recording medium by a partial response signal processing method and a demodulating means for demodulating the equalized information signal. When the γ indicating the asymmetry of the isolated inverted reproduction waveform reproduced from the magnetic recording medium has a waveform where γ> 0, the demodulating unit is configured to equalize the information signal by the equalizing unit. The coefficient terms (1, a ₁ , a ₂ ,..., A _m (m = 2n or 2n + 1: n is an integer equal to or greater than 1)) for the partial response for the above formula (1) or (2) When demodulating under a satisfying condition and the γ has a waveform with γ <0, the demodulating means includes a partial response coefficient term (1, a) for the information signal equalized by the equalizing means. _1, a _2, ··, a _{m (m} = 2n or 2n + 1: n is an integer of 1 or more) to provide a recording and reproducing apparatus characterized by) demodulates the condition satisfying the formula (3) or formula (4) below.

  In this recording / reproducing apparatus, according to the asymmetry of the isolated inverted reproduction waveform reproduced from the magnetic recording medium, the sum of the first half of the coefficient terms of the partial response for the information signal equalized by the equalizing means The demodulating means demodulates the information signal so that the sum of the latter term satisfies the above formulas (1) and (2) or the above formulas (3) and (4). It is possible to perform the partial response signal processing optimal for the characteristics of the magnetic material.

In the present invention, γ indicating the asymmetry of the isolated inverted reproduction waveform reproduced from the magnetic recording medium is an index indicating whether the peak position of the isolated inverted reproduction waveform is biased to the first half waveform portion or the second half waveform portion. For example, when the half-value width of the left-right asymmetric isolated inverted reproduction waveform shown in FIG. 2 is PW50, the right-side width of the half-value width PW50 is PW1, and the left-side width is PW2, the following expression (5) is expressed. Say the ratio.
γ (%) = [[(PW1) − (PW2)] ÷ (PW50)] × 100 (5)

  Furthermore, the present invention provides a magnetic recording medium used for the recording / reproducing apparatus.

  The recording / reproducing method and recording / reproducing apparatus of the present invention perform partial response signal processing optimal for the characteristics of the magnetic material forming the magnetic layer of the magnetic recording medium when reproducing the information signal recorded on the magnetic recording medium, A reproduction signal having a high S / N ratio can be obtained from a magnetic recording medium on which information is recorded at high density. Therefore, a reproduction signal can be obtained at a low error rate. In particular, in the case of a magnetic recording medium using a hexagonal ferrite magnetic material, the characteristics of the hexagonal ferrite magnetic material, such as high reproduction output at high density recording and low noise, can be utilized.

  Further, the magnetic recording medium of the present invention exhibits the characteristics of the magnetic material by performing the partial response signal processing optimum for the characteristics of the magnetic material forming the magnetic layer in the recording / reproducing apparatus, thereby providing high-density information. Can be recorded, and a reproduction signal having a high S / N ratio can be obtained. Therefore, a reproduction signal can be obtained at a low error rate.

The recording / reproducing method, recording / reproducing apparatus, and magnetic recording medium of the present invention will be described below.
The magnetic recording medium of the present invention has a magnetic layer containing a magnetic material to which an information signal is written by a recording head of a recording / reproducing apparatus on one or both sides of a support, and a nonmagnetic layer is formed under the magnetic layer. It is what you have. As a specific example of this magnetic recording medium, an information signal is remanently magnetized by a magnetic recording head on a magnetic layer containing a magnetic material such as a magnetic tape, a magnetic disk (hard disk, flexible disk), a ferromagnetic alloy powder containing Fe as a main component. A recording medium that can be recorded in a form is mentioned.

  Supports include polyethylene terephthalate, polyethylene, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamideimide, polyimide, polysulfone, polyethersulfone, and other synthetic resins, and films and plates made of metals such as aluminum and stainless steel. Or the like can be used according to the application, form, etc. of the magnetic recording medium.

When the magnetic recording medium is in sliding contact with the recording head or the reproducing head, the magnetic recording medium preferably has a back layer that makes the sliding contact smooth on the surface of the support opposite to the magnetic layer.
The magnetic recording medium may have a layer other than the nonmagnetic layer, the magnetic layer, and the back layer. For example, it may have a soft magnetic layer containing soft magnetic powder, a second magnetic layer, a cushion layer, an overcoat layer, an adhesive layer, and a protective layer. These layers can be provided at appropriate positions so that their functions can be effectively exhibited. The thickness of the magnetic layer is preferably 10 to 300 nm, more preferably 10 to 200 nm, and particularly preferably 10 to 100 nm. The nonmagnetic layer can be 0.5 to 3 μm. The nonmagnetic layer is preferably thicker than the magnetic layer.

As the magnetic material, ferromagnetic metal powder or hexagonal ferrite powder is used.
Specific examples of the ferromagnetic metal powder include simple metals or alloys such as Fe, Ni, Fe—Co, Fe—Ni, Co—Ni, Co—Ni—Fe, and the range of 20% by mass or less of the metal component. Within, aluminum, silicon, sulfur, scandium, titanium, vanadium, chromium, manganese, copper, zinc, yttrium, molybdenum, rhodium, palladium, gold, tin, antimony, boron, barium, tantalum, tungsten, rhenium, silver, lead , Phosphorus, lanthanum, cerium, praseodymium, neodymium, tellurium, bismuth, and the like. The ferromagnetic metal powder may contain a small amount of water, hydroxide or oxide.

  The average particle size of the ferromagnetic powder is preferably 20 to 60 nm. When the ferromagnetic powder to be used is needle-shaped or the like, the average major axis length is 30 to 100 nm, preferably 35 to 90 nm, and more preferably 40 to 80 nm. By setting the average major axis length to 100 nm or less, noise can be reduced and a good signal SN can be obtained. Moreover, favorable holding power Hc can be ensured by setting the average major axis length to 30 nm or more. The average acicular ratio of the powder particles is 3 to 10, preferably 3 to 8, and more preferably 4 to 8. In the case of a plate shape, the average powder size is expressed by an average plate diameter, preferably 25 to 35 nm, and the average plate ratio is preferably 2 to 5.

The ferromagnetic metal powder has an S _BET (BET specific surface area) of usually 40 to 80 m ² / g, preferably 50 to 70 m ² / g. The crystallite size is usually 10 to 25 nm, preferably 11 to 22 nm. The pH of the ferromagnetic metal powder is preferably 7 or more.

  These ferromagnetic metal powders can be produced according to known methods. Although there is no restriction | limiting in particular in the shape of a ferromagnetic metal powder, Usually, a needle shape, a granular form, a dice shape, a rice granular shape, a plate shape etc. are used. In particular, it is preferable to use acicular ferromagnetic powder.

The coercive force Hc of the ferromagnetic metal powder is preferably 144 to 300 kA / m, and more preferably 160 to 224 kA / m. Further, the saturation magnetization is preferably 85~150A · m ² / kg, more preferably 100~130A · m ² / kg.

  Examples of the hexagonal ferrite include barium ferrite, strontium ferrite, lead ferrite, calcium ferrite, and various substitutes thereof, for example, Co substitutes. Specific examples include magnetoplumbite-type barium ferrite and strontium ferrite, magnetoplumbite-type ferrite whose particle surface is coated with spinel, and composite magnetoplumbite-type barium ferrite and strontium ferrite partially containing a spinel phase. In addition to predetermined atoms, Al, Si, S, Nb, Sn, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, W, Re, Au, Bi, It may contain atoms such as La, Ce, Pr, Nd, P, Co, Mn, Zn, Ni, B, Ge, and Nb. In general, Co-Zn, Co-Ti, Co-Ti-Zr, Co-Ti-Zn, Ni-Ti-Zn, Nb-Zn-Co, Sn-Zn-Co, Sn-Co-Ti, Nb-Zn, etc. The thing which added these elements can be used. It is also possible to use W-type hexagonal ferrite. Furthermore, the thing containing the characteristic impurity originating in a raw material and a manufacturing method may be used. These hexagonal ferrites are used in the form of hexagonal plate-like powder.

By setting the average plate diameter of the hexagonal ferrite magnetic powder to 50 nm or less and the average thickness to 15 nm or less, noise can be reduced and high S / N can be obtained when reproducing with high-density recording, particularly with an MR head. The specific surface area according to the BET method is usually 30 to ²⁰⁰ m ² / g, and preferably 50 to 100 m ² / g. The specific surface area generally agrees with the arithmetic calculation value from the powder plate diameter and plate thickness. The narrower the distribution of plate diameter and plate thickness, the better. In many cases, the distribution is not a normal distribution. When expressed as a standard deviation with respect to the powder size, σ / (average plate diameter or average plate thickness) = 0.1 to 0.5. In order to sharpen the powder size distribution, the powder production reaction system is made as uniform as possible, and the produced powder is subjected to a distribution improving process. For example, a method of selectively dissolving ultrafine powder in an acid solution is also known. In the vitrification crystal method, a more uniform powder is obtained by performing heat treatment a plurality of times to separate nucleation and growth. The coercive force Hc measured with the magnetic powder can be made up to about 40 to 400 kA / m, but preferably 144 to 300 kA / m. Higher Hc is more advantageous for high density recording, but is limited by the capacity of the recording head. Hc can be controlled by the powder size (plate diameter / plate thickness), the type and amount of the contained element, the substitution site of the element, the powder production reaction conditions, and the like.

The saturation magnetization σS of the hexagonal ferrite powder is preferably 30 to 70 A · m ² / kg. σS tends to decrease as the powder becomes finer.

  In the present invention, a coated barium ferrite (BaFe) magnetic layer in which a magnetic layer is formed by coating a dispersion containing a barium ferrite powder of hexagonal ferrite on a support, particularly a barium ferrite magnetic layer having a plate diameter of 40 nm or less. A magnetic recording medium having a coated barium ferrite magnetic layer using a body is effective because it has excellent reproduction output in high-density recording (particularly linear recording density exceeding 100 kfci) and has low noise characteristics. .

  In general, in a magnetic recording medium using iron oxide or cobalt-containing ferromagnetic iron oxide as a magnetic material, the isolated inversion reproduction waveform to be reproduced shows asymmetry of γ≈0, and hexagonal ferrite is used as the magnetic material. In the conventional magnetic recording medium, the isolated inverted reproduction waveform to be reproduced exhibits asymmetry of γ> 0. Further, in a magnetic recording medium having a magnetic layer formed by vapor deposition, the isolated inverted reproduction waveform to be reproduced exhibits a relative symmetry of γ <0. Therefore, according to this asymmetry, the partial response signal processing is equalized so as to satisfy the conditions represented by the above (1) and (2) or (3) and (4). Optimal partial response signal processing can be performed according to the magnetic material forming the magnetic layer.

That is, in the recording / reproducing method and recording / reproducing apparatus of the present invention, when reproducing an information signal from the magnetic recording medium, first, an analog signal read from the magnetic recording medium by the recording / reproducing head is used for the magnetic recording medium. Depending on the magnetic material, it can be preliminarily estimated whether γ indicating the asymmetry of the isolated inverted reproduction waveform is γ> 0, γ≈0, or γ <0. Therefore, in the recording / reproducing method and recording / reproducing apparatus of the present invention, when γ indicating asymmetry of the isolated inverted reproduction waveform to be reproduced has a waveform in which γ> 0, depending on the magnetic material of the magnetic recording medium to be used. Is a partial response coefficient term (1, a ₁ , a ₂ ,..., A _m (m = 2n or 2n + 1: n is an integer of 1 or more) satisfies the above formula (1) or (2). Under certain conditions, the information signal read from the magnetic recording medium is equalized by the partial response signal processing method, and the equalized signal is demodulated to restore the original signal. , Which has an asymmetry of γ <0, the partial response coefficient terms (1, a ₁ , a ₂ ,..., A _m (m = 2n or 2n + 1: n is 1). The above integer) is the above formula (3 Alternatively, the information signal read from the magnetic recording medium is equalized by the partial response signal processing method under the condition satisfying Expression (4), and the equalized signal is demodulated to restore the original signal. Thus, the optimum partial response signal processing, that is, PR4ML (PR (1,0, -1) ML), EPR4ML (PR (1,1, -1, -1) ML), EEPR4ML (PR (1, 2, 0, -2, -1) ML), EEEPR4ML (PR (1, 3, 2, -2, -3, -1) ML), etc. By selecting whether to perform equalization processing by the partial response signal processing method, the reproduction signal can be restored at a low error rate.

Next, taking a magnetic recording medium having a magnetic layer containing barium ferrite as a magnetic material as an example, the recording / reproducing method and recording / reproducing apparatus of the present invention will be described with reference to FIGS.
FIG. 1 shows a configuration example of a recording / reproducing apparatus according to the present invention. This recording / reproducing apparatus 10 includes a precoder 11, a recording / reproducing amplifier 12, a recording head 13, a reproducing head 14, and an equalizer (equalization). Means) 15, a maximum likelihood decoder 16, and a decoder (demodulation means) 17.

  By placing the precoder 11 before data recording, it is possible to prevent propagation of errors that occur during demodulation.

The recording / reproducing amplifier 12 amplifies the signal encoded by the precoder 11 and amplifies the signal generated by the reproducing head 14 described later.
The recording head 13 magnetizes barium ferrite magnetic material contained in the magnetic layer of the magnetic recording medium 20 and records data of a predetermined clock period on the magnetic recording medium 20.

  The reproducing head 14 is in sliding contact with the magnetic layer of the magnetic recording medium 20, reads the change in magnetization of the magnetic layer, and obtains an analog reproduction signal. This analog signal is a signal obtained by differentiating the signal recorded on the magnetic layer of the magnetic recording medium 20, and is represented by a transfer characteristic of (1-D).

  An example of a waveform of an analog signal generated by reading by the reproducing head 14 is shown in FIG. Here, an isolated inverted reproduction waveform generated at the rising timing of the pulse signal recorded on the magnetic recording medium 20 will be described as an example.

  The isolated inverted reproduction waveform shown in FIG. 2 has a peak in the positive direction, and the left and right sides of the peak are asymmetric. In this isolated inverted reproduction waveform, the right-side width PW1 of the half-value width PW50 of the peak value is larger than the left-side width PW2. This is the sum of the in-plane orientation magnetization component and the perpendicular magnetization component peculiar to barium ferrite.

  In FIG. 2, the isolated inverted reproduction waveform having a peak in the positive direction is shown as an analog signal waveform. However, in reality, the waveform of the analog signal has two isolated inverted reproductions having peaks in the positive direction and the negative direction. It is composed of overlapping waveforms. This is because an isolated inverted reproduction waveform having a peak in the negative direction is also generated at the falling timing of the pulse signal recorded on the magnetic recording medium 20.

The equalizer 15 (equalizing means) equalizes the signal transferred from the reproducing head 14 via the recording / reproducing amplifier 12. PR (1, a, b, c, d, e,...) Has a transfer characteristic of 1 + a · D + b · D ² + c · D ³ + d · D ⁴ + e · D ⁵ +... = (1-D) When (1 + f ₁ · D + f ₂ · D ² + f ₃ · D ³ + f ₄ · D ⁴ +...), Specifically, the equalizer 15 has a transfer characteristic of 1 + f ₁ · D + f ₂ · D ² + f _3. Equalize as represented by D ³ + f ₄ · D ⁴ +.

  The maximum likelihood decoder 16 identifies the data equalized by the equalizer 15. Maximum likelihood decoding is a well-known technique for detecting the most probable data sequence when data is recorded and reproduced with correlation. Then, the decoder 17 decodes the equalized signal into original data (for example, (0, 1, 0)). As a result, the recording data recorded on the magnetic recording medium 20 can be correctly restored to the original data.

  Hereinafter, an example in which the recording / reproducing method of the present invention is specifically performed will be described.

<Prescription of coating solution for BaFe magnetic layer>
Barium ferrite magnetic powder 100 parts Polyurethane resin 14 parts Weight average molecular weight: 10,000
Sulfonic acid functional group: 0.05 meq / g
Abrasive 8 parts carbon black (particle size: 0.015 μm) 0.5 parts # 55 (Asahi Carbon Co., Ltd.)
Stearic acid 0.5 part Butyl stearate 2 parts Methyl ethyl ketone 180 parts Cyclohexanone 100 parts

<Prescription of coating solution for nonmagnetic layer>
Nonmagnetic powder: α iron oxide 100 parts Average primary particle size: 0.09 μm, specific surface area by BET method: 50 m ² / g
pH: 7 DBP oil absorption: 27-38 ml / 100 g,
Surface treatment layer: Al ₂ O ₃ is present in an amount of 8% by mass based on the whole particle 25 parts of carbon black Conductex SC-U (manufactured by Columbian Carbon)
Vinyl chloride copolymer: MR104 (manufactured by Nippon Zeon Co., Ltd.) 13 parts Polyurethane resin: UR8200 (manufactured by Toyobo Co., Ltd. 9 parts 5 parts phenylphosphonic acid 3.5 parts butyl stearate 1 part stearic acid 2 parts methyl ethyl ketone 205 parts cyclohexanone 135 parts

<Manufacture of tape>
Each component was kneaded with a kneader according to the formulation of the coating solution. The obtained kneaded liquid was pumped through a horizontal sand mill filled with 1.0 mmφ zirconia beads in an amount of 80% with respect to the volume of the dispersion part, and remained at 2000 rpm for 120 minutes (substantially stayed in the dispersion part. Time) Dispersion treatment was performed to prepare a dispersion for the magnetic layer and a dispersion for the nonmagnetic layer, respectively. To the obtained dispersion for magnetic layer, 3 parts of methyl ethyl ketone was further added and filtered using a filter having an average particle diameter of 1 μm to obtain a coating solution for forming a magnetic layer. Further, 2.5 parts of polyisocyanate and 3 parts of methyl ethyl ketone are added to the dispersion for the nonmagnetic layer, and the mixture is filtered using a filter having an average particle diameter of 1 μm to form a coating liquid for forming the nonmagnetic layer. Were prepared respectively.

  The obtained coating solution for forming a nonmagnetic layer was applied onto a polyethylene naphthalate base having a thickness of 4 μm so that the thickness after drying was 1.5 μm and dried to form a nonmagnetic layer. After that, the magnetic layer forming coating solution is successively applied onto the nonmagnetic layer so that the thickness of the magnetic layer is 30 to 210 nm, and the magnetic layer has a magnetic force of 600 mT while it is still wet. A BaFe magnetic body in the magnetic layer is oriented in the plane by a cobalt magnet and a solenoid having a magnetic force of 600 mT, and a magnetic field is applied obliquely by applying a magnetic field in the vertical direction with a 600 mT cobalt magnet. The vertical magnetic field was maintained until drying was completed. Next, the treatment was carried out with a seven-stage calendar at a temperature of 90 ° C. and a linear pressure of 300 kg / cm (294 kN / m). Thereafter, a back layer forming layer coating solution having the following formulation was applied to the surface opposite to the surface on which the nonmagnetic layer and the magnetic layer were formed to form a back layer having a thickness of 0.5 μm to obtain a web original fabric. .

Back layer forming coating solution Carbon black (average particle size: 17 nm) 100 parts Calcium carbonate (average particle size: 40 nm) 80 parts α-alumina (average particle size: 200 nm) 5 parts Dispersion liquid (nitrocellulose resin, polyurethane resin, poly Isocyanate)

  As described above, an apparatus having a non-magnetic layer and a magnetic layer on one side and a web web having a back layer on the other side is slit to a width of 3.8 mm, and includes a delivery unit and a winding unit for slit products. The nonwoven fabric and the razor blade were attached so as to press against the magnetic surface, and the surface of the magnetic layer was cleaned with a tape cleaning device to obtain a magnetic tape having a magnetic layer containing a BaFe magnetic material.

  Data waveforms having different normalized linear densities K = (PW50) / (bit length) are recorded on a magnetic tape having a magnetic layer containing a BaFe magnetic material using the recording / reproducing apparatus having the configuration shown in FIG. Three types of playback samples were prepared. For the isolated inverted reproduction waveform (γ = 22%) reproduced from each of these three types of magnetic tapes, PR (1, a, b, c) ML system, PR (1, a, b, c, d) With the ML method and the PR (1, a, b, c, d, e) ML method, an error rate with a coefficient in which the absolute value of the sum of the first half of the characteristic term is smaller than the absolute value of the sum of the second half of the term is obtained. It was measured. Further, the normal PRML system (= PR (1,1, -1, -1) ML system, PR (1,2,0, -2, -1) ML system, PR (1,3,2, -2) , -3, -1) ML method) was also measured.

The same applies to magnetic tapes using metal (ferromagnetic alloy powder containing Fe as a main component, γ = 3%) and ME (magnetic layer by vapor deposition, γ = -13%) magnetic tape as magnetic materials. The error rate was measured.
The obtained results are shown in Table 1.

表１に示す結果から、γ（＝２２％）＞０であるバリウムフェライト（ＢａＦｅ）磁性体およびγ（＝３％）＞０であるメタル（Ｆｅを主成分とする強磁性合金粉末）磁性体を用いた磁気テープでは、前記式（１）または（２）の場合にエラーレートが低減することが分かった。
また、γ（＝−１３％）＜０であるＭＥ（蒸着法による磁性層）磁気テープでは、前記式（３）または（４）の場合にエラーレートが低減することが分かった。

From the results shown in Table 1, barium ferrite (BaFe) magnetic material with γ (= 22%)> 0 and metal (ferromagnetic alloy powder containing Fe as a main component) magnetic material with γ (= 3%)> 0 It was found that the error rate is reduced in the case of the above formula (1) or (2) in the magnetic tape using.
Further, it was found that the error rate is reduced in the case of the formula (3) or (4) in the ME (magnetic layer by vapor deposition method) magnetic tape in which γ (= −13%) <0.

It is a block diagram which shows the structural example of the recording / reproducing apparatus of this invention. It is a figure which shows an example of an isolated inversion reproduction | regeneration waveform. It is a figure which shows an example of the signal series in a partial response signal process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Recording / reproducing apparatus 11 Precoder 12 Recording / reproducing amplifier 13 Recording head 14 Reproducing head 15 Equalizer 16 Maximum likelihood decoder 17 Decoder 20 Magnetic recording medium

Claims (9)

A recording / reproducing method for equalizing and demodulating an information signal recorded on a magnetic recording medium by a partial response signal processing method,
An information signal having a waveform in which γ representing the asymmetry of the isolated inverted reproduction waveform reproduced from the magnetic recording medium is γ> 0 is expressed as a partial response coefficient term (1, a ₁ , a ₂ ,..., A A recording / reproducing method, wherein _m (m = 2n or 2n + 1: n is an integer of 1 or more)) is equalized and demodulated under a condition satisfying the following expression (1) or expression (2).

  2. The recording / reproducing method according to claim 1, wherein the magnetic recording medium has a magnetic layer containing hexagonal ferrite.   The recording / reproducing method according to claim 2, wherein the hexagonal ferrite is barium ferrite. A recording / reproducing method for equalizing and demodulating an information signal recorded on a magnetic recording medium by a partial response signal processing method,
An information signal having a waveform in which γ representing the asymmetry of the isolated inverted reproduction waveform reproduced from the magnetic recording medium is γ <0 is represented by a coefficient term (1, a ₁ , a ₂ ,..., A A recording / reproducing method, wherein _m (m = 2n or 2n + 1: n is an integer of 1 or more)) is equalized and demodulated under a condition satisfying the following expression (3) or expression (4).

A recording / reproducing apparatus having equalization means for equalizing an information signal recorded on a magnetic recording medium by a partial response signal processing method, and a demodulation means for demodulating the equalized information signal,
When γ indicating the asymmetry of the isolated inverted reproduction waveform reproduced from the magnetic recording medium has a waveform with γ> 0, the demodulating means performs partial processing on the information signal equalized by the equalizing means. Response coefficient terms (1, a ₁ , a ₂ ,..., A _m (m = 2n or 2n + 1: n is an integer greater than or equal to 1)) satisfy the following formula (1) or formula (2) A recording / reproducing apparatus for demodulating.

  6. The recording / reproducing apparatus according to claim 5, wherein the magnetic recording medium has a magnetic layer containing hexagonal ferrite.   The recording / reproducing apparatus according to claim 6, wherein the hexagonal ferrite is barium ferrite. A recording / reproducing apparatus having equalization means for equalizing an information signal recorded on a magnetic recording medium by a partial response signal processing method, and a demodulation means for demodulating the equalized information signal,
When γ indicating the asymmetry of the isolated inverted reproduction waveform reproduced from the magnetic recording medium has a waveform where γ <0, the demodulating means performs partial processing on the information signal equalized by the equalizing means. Response coefficient terms (1, a ₁ , a ₂ ,..., A _m (m = 2n or 2n + 1: n is an integer greater than or equal to 1)) satisfy the following formula (3) or formula (4) A recording / reproducing apparatus for demodulating.

  The magnetic recording medium used for the recording / reproducing apparatus of any one of Claims 5-8.

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